Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Accumulated Amortization	$ (24,090)		$ (24,090)		$ (22,598)
Intangible Assets, Net (Including Goodwill)	55,457		55,457		59,907
Finite-Lived Intangible Assets, Net	40,488		40,488		44,433
Finite-Lived Intangible Assets, Gross	64,578		64,578		67,031
Intangible Assets, Gross (Excluding Goodwill)	79,547		79,547		82,505
Indefinite-Lived Trademarks	14,969		14,969		15,474
Intangible Assets, Net (Excluding Goodwill)	55,457		55,457		59,907
Goodwill	40,294		40,294		$ 40,294
Amortization of Intangible Assets	1,100	$ 1,400	2,300	$ 2,300
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	4,500		4,500
Finite-Lived Intangible Assets, Amortization Expense, after Year Five	17,800		$ 17,800
Purchased Technology Customer Relationships And Patents [Member] | Weighted Average [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life			15 years 9 months 12 days		15 years 9 months 12 days
Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Accumulated Amortization	(11,335)		$ (11,335)		$ (10,625)
Finite-Lived Intangible Assets, Net	15,327		15,327		16,037
Finite-Lived Patents, Gross	26,662		26,662		26,662
Amortization of Intangible Assets	400	300	700	700
Finite-Lived Intangible Assets, Amortization Expense, after Year Five	8,200		8,200
Finite-Lived Intangible Assets, Amortization Expense, Year Four	1,400		1,400
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Accumulated Amortization	(12,531)		(12,531)		(11,735)
Finite-Lived Intangible Assets, Net	25,161		25,161		28,396
Finite-Lived Customer Relationships, Gross	37,692		37,692		$ 40,131
Amortization of Intangible Assets	800	$ 1,100	$ 1,600	$ 1,600
Finite-Lived Intangible Asset, Useful Life			12 years 3 months 12 days		12 years 3 months 12 days
Finite-Lived Intangible Assets, Amortization Expense, after Year Five	9,600		$ 9,600
Finite-Lived Intangible Assets, Amortization Expense, Year Four	3,100		3,100
Other Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Accumulated Amortization	(224)		(224)		$ (238)
Finite-Lived Intangible Assets, Net	0		0		0
Other Finite-Lived Intangible Assets, Gross	224		224		238
Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Net (Excluding Goodwill)	$ 14,969		$ 14,969		$ 15,474